Oriented saran coextrudate

ABSTRACT

An oriented two-layered laminate of vinylidene chloride-vinyl chloride copolymer as one layer and an ethylene-unsaturated ester type copolymer as the other layer. To this laminate may be adhered another polymer, also capable of being oriented, plastic sheet, paper sheet or board, metal or metal foil. Products such as pouches, chubs, formed troughs and the like can be made therefrom because the vinylidene chloride-vinyl chloride copolymer retains its orientation.

This is a division of application Ser. No. 237,953, filed Mar. 24, 1972,now U.S. Pat. No. 3,924,051, which in turn was a continuation of Ser.No. 70,524, filed Sept. 8, 1970, now abandoned which in further turn wasa continuation of Ser. No. 630,889, filed Apr. 14, 1967 now abandoned.

This invention relates to a unique oriented basic laminate of avinylidene chloride-vinyl chloride copolymer and an ethylene-unsaturatedester type copolymer. The basic laminate may have adhered theretoanother polymer, or a paper or metal product such as paper sheet orboard, foil and the like. This invention also relates to the method andthe apparatus for preparing the laminate, for adhering another polymer,or a paper or metal product thereto and the articles produced therefrom.

The use of films of vinylidene chloride-vinyl chloride copolymer, morecommonly known as "saran", has become extremely popular due to thephysical characteristics of the film. It is clear, of high tensilestrength, forms a good barrier against moisture and vapor transmission,is mildew resistant, has good conformability to the item being wrapped,may be formulated for high slip, and uniquely possesses an inherentself-adherability, or "cling". It is this latter feature coupled withthe other desirable characteristics mentioned that has made it mostattractive and readily accepted for the wrapping of food.

To acquire these desirable characteristics, the saran film must beoriented. This is accomplished by extruding it in the form of a tube,supercooling, and then blowing the tube outwardly whereby the moleculesmaking up the copolymer are oriented in a pattern other than merely thatof the extrusion flow pattern.

Unfortunately, orientation is adversely affected by heat. Because ofsuch loss of orientation, an instantaneous film shrinking occurs. Thus,heat seals are not smooth and a weak seal results. Furthermore, hot meltcoating of oriented saran film with other polymeric or copolymericmaterial to produce a film of more desirable characteristic is notpossible. The oriented saran film loses its orientation upon contactwith hot melt. In lamination, the hot press rolls usually used cause thesaran to act similarly. And, in vacuum forming, saran loses some of itsorientation because of the heat necessary to soften it for the draw and"pinholes".

An object of this invention is to provide a novel saran film.

Another object is to provide a saran film laminate capable of beingbubble oriented.

Still another object is to provide a method for making said saran filmlaminate.

A further object is to provide apparatus for making the saran filmlaminate.

A still further object is to provide a saran film laminate which retainsits desirable orientation characteristics even when heat-worked.

Another object is to provide a saran film, of the above characteristics,capable of being heat sealed.

Another object is to provide a saran film of the above characteristicswhich acts differently to solvents and chemicals on each of its sides.

Another object is to provide a saran film of the above characteristicscapable of being vacuum drawn.

Another object is to provide a saran film capable of being heatlaminated to paper, plastic, or metal.

Another object is to provide a saran coated paper useful as bottle capliner material.

Another object is to provide a saran laminate useful for form, fill andseal packaging.

Another object is to provide a film laminate useful as a cheese curingblock overwrap.

Another object is to provide a film laminate useful as a heat sealableshrink overwrap.

Another object is to provide a saran wrapping material which ispre-labeled.

Another object is to provide a method for easily making such pre-labeledsaran wrapping material.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

It has now been found that vinylidene chloridevinyl chloride copolymer,or "saran" as it is more commonly called in the trade, may be coatedwith an ethylene-unsaturated ester type copolymer by coextruding saidcopolymers as a tube. Similar or completely different polymericmaterials may also be extruded as further layers thereon, if desired. Inany event, the coextrudate is then immediately immersed in one or moretempering baths to chill and to provide a proper blow temperature forthe coextrudate. The tube is subsequently blown into a bubble to orientthe molecules of the plastic, especially the vinylidene chloridevinylchloride copolymer molecules which appear to be the main componentsenabling bubble orientation. Indeed, in the past, it was believed thatthe behavior of the ethyleneunsaturated ester type copolymer wouldprobably not permit orientation of the saran, at least to the highdegree (up to 16 times) of bilateral orientation that is accomplished bythe method of the invention. Now, surprisingly, the manner ofcoextrusion, coupled with the application of correct temperature wherebychilling and reheating of the unoriented tube to just the righttemperature, uniquely enables orientation of the entire laminate.Apparently, this is the only way an oriented, coated, saran film can beobtained, since post-coating on oriented saran distorts and deorientsthe film.

The laminate may then be rolled onto a wind-up roll, or subsequentlyprocessed. Subsequent processing may involve lamination to paper,plastic, or metal with the ethylene-unsaturated ester type copolymer plyacting as the adhesive. It may also involve vacuum drawing of the film.The laminate may also be used in the packaging process known as "form,fill and seal", because it is heat sealable. In fact, it is heatsealable at a much lower temperature (180° F) and the seal is strong.This favorably compares to the very weak seal of saran over a narrowerrange (260° to 280° F). The resultant film of this invention may also bepre-labeled by a "trap label" process wherein a continuous array ofindividual labels may be trapped between two layers of basic laminatewith ethylene-unsaturated ester type copolymer ply of each being adheredtogether. The resulting label laminate may then be formed and sealedusing either high frequency or usual heat sealing methods, depending onthe layer structure.

More particularly, a unique saran can now be made by coextrudingvinylidene chloride-vinyl chloride copolymer as one layer with anethylene-unsaturated ester type copolymer such as ethylene-vinylacetate, ethylene-vinyl propionate, ethylene-methyl methacrylate,ethylene-ethyl methacrylate, ethylene-ethyl acrylate, ethylene-isobutylacrylate, as the second layer. Additional layers may also be coextrudedalong with the above mentioned copolymers to effect a variation in thedesired characteristics in the film. The laminate, immediately followingextrusion, is chilled at 5° to 25° C and then tempered at 20° to 50° Cvia a cooling and a heating bath respectively for subsequent blowing ofthe tube to effect orientation of the plastic molecules. Afterorientation, the film is wound for subsequent use or immediatelylaminated to other web stock such as paper, or plastic or metal; vacuumdrawn, or used directly in a packaging operation such as form, fill andseal, or as a cheese block curing overwrap or other packaging processes.

The invention accordingly comprises an article of manufacture possessingthe features, properties, and the relation of elements which will beexemplified in the article hereinafter described, and the several stepsand the relation of one or more of such steps with respect to each ofthe others thereof which will be exemplified in the method hereinafterdisclosed, and the features of construction, combination of elements,and arrangement of parts which will be exemplified in the constructionhereinafter set forth, and the scope of the invention will be indicatedin the claims.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawing, in which:

FIG. 1 is a perspective view of a preferred embodiment of apparatus forpreparing the basic laminate of this invention.

FIG. 2 is a side cross-sectional view of the extrusion die head of theapparatus shown in FIG. 1, taken along line 2--2. FIG. 3 is a sidecross-sectional view of another embodiment of an extrusion die head thatmay be utilized.

FIGS. 4 and 4a perspective are views of laminating apparatus showing thebasic laminate of the invention being laminated to paper, and eitherwound on a wind-up roll or else punched into bottle cap liners.

FIGS. 5 and 5a are perspective views of laminating apparatus wherein thebasic laminate is labeled via a label trapping technique (FIG. 5) andthen formed into a chub (FIG. 5a).

FIG. 6 shows a variation of the pre-labeled material of FIG. 5 whereinthe labels are discontinuous.

FIG. 7 is a perspective view showing the basic laminate used as a cheesecuring block overwrap.

FIG. 8 is a perspective view showing the paper laminated version of thebasic saran laminate used for form, fill and seal packaging.

FIG. 9 is a perspective view showing the basic laminate vacuum formed toproduce a continuous array of shallow troughs.

Similar reference characters refer to similar parts throughout theseveral views of the drawings.

The various elements shown in the various figures of the drawing will beexplained hereinafter, along with recitation of specific Examples whichillustrate the method of making the basic laminate, with or withoutadditional plies, its lamination with and the use of the basic laminate,the added ply laminate and the paper laminate.

EXAMPLE I PRODUCTION OF BASIC LAMINATE

As indicated above, the basic laminate is made of a ply of vinylidenechloride-vinyl chloride copolymer and a ply of ethylene-unsaturatedester type copolymer.

In making this laminate, a slightly modified form of the apparatus ofFIGS. 1 to 3 may be utilized, as explained below.

The apparatus in FIG. 1, comprises an extrusion die head 10 having aplurality of annular extrusion slits (12, 14 and 16), in the twoembodiments shown in FIGS. 2 and 3. It should be understood that for thebasic laminate, only two slits are actually used. The third slit may beblocked, with a gasket at the lips of the slit.

Since saran is adversely affected by prolonged exposure to hightemperature, extrusion slit 12 is preferably designed without a slitfeed manifold. Instead, a streamlined flow slit feed 18, leading fromthe saran extruder barrel 20 to the slit 12 is utilized. The otherplastic feed means utilize manifolds 22 and 24 which feed slits 14 and16 respectively. A manifold is used with ethylene-unsaturated ester typecopolymers because it is stable to the temperature encountered in theextrusion.

It might be noted from a comparison of the structures shown in FIGS. 2and 3, that in FIG. 2 the saran is extruded as the internal ply, whereasin FIG. 3, the saran is extruded as the second or middle ply.

It will also be noted that slits 12, 14 and 16 blend into a singularannular exit slit 17 out of which the laminate 30 exudes as a tube orsock 32. The sock enters a cooling bath 34, maintained at 5° to 25° C tosupercool the plastic in the laminate. Squeeze rolls 36 flatten the sock32 into a lay flat form. The tube 32 then exits the cooling bath 34,travels over guide-squeeze rolls 38, and then into a heating bath 40,maintained at 20° to 50° C, or at another temperature sufficient to heatthe plastic whereby it may be expanded and properly crystallized ororiented. Both baths may be contained in a double compartmented tank 42.

The tube 32 travels around guide roll 44 immersed in bath 40. It thenleaves bath 40 in a heat-softened condition and travels between bubbleseal rolls 46. The tube is then expanded into a plastic bubble 48 viasuperatmospheric pressure injected into the tube 32 in the customarymanner well known in the trade.

To aid in regulating the degree of expansion of the tube, a cooling ring54 with jet orifices 56 therein may be used to blast cool air or gasagainst the outside of the bubble to aid in setting or hardening thesecondary plastic of the tube 32 at the desired degree of expansion. Theair or gas is supplied to the cooling ring from inlet 58.

Expansion of the tube causes orientation of the molecules of theplastic.

After blowing, the tube is flattened via a series of converging rollers58, and pinch rolls 60. The tube is then wound on windup roll 62 or useddirectly in converting processes.

With respect to the method of this invention, it might be noted thataccording to the theory of multiple-layer, bubble-oriented extrusion,laminar flow will prevail when two viscous molten polymers are extrudedsimultaneously from the same die. For example, when a center rod ofsaran, surrounded by another polymer, is forced through a sheet die, theflow causes the saran to remain at the center of the other polymer in auniform layer. Unfortunately, the same does not apply when it is forcedinto and through a crosshead tube die. Here the normally uniform flow issplit. So, the polymer must be distributed in tube fashion on theoutside of an already tube-formed saran. The apparatus just describedand illustrated in FIG. 1 accomplishes such.

With the two die head arrangements in FIGS. 2 and 3, the distribution ofthe polymer about the saran is excellent. The means for discerningwhether distribution was good can be determined by (1) the symmetry ofthe resultant bubble, (2) the total gauge measurement of the resultantfilm across the web, and (3) individual layer thickness by microscopy,and (4) relative flow ratios of the extruders.

Table I, which follows, sets forth a series of runs:

    TABLE I      TWO LAYER LAMINATE               Film                 Tensile     -18*Dart      Secondary     Strength     Drop   Elec-  Film Secondary Secondary Saran Film   PSI     Impact  Heat tronic Run Polymer Extrusion Extrusion Thickness Thickness     Extrud- Film .sup.(14) (in. Film % Film O.sub.a Gas Cold (gm) (13)     100°      C Seals Bag No. Type Rate Rate (Gauge) (Gauge) ability.sup.(1) Bond.sup.     (2) Thousand) Elongation Clarity.sup.(3) Transmission Flex Saran Shrink     lbs./in Seals       L(11) C(12) L C Up L C Peel Sheer 1 ET-.sup.(4)                    33%     VA 13 4-7 50-100 20-70 G.sup.(8) E.sup.(9)     E  1 50 100   3-4 5-10 2     ET-  28% VA 13 4-6 50-100 20-70 G E 9.0 9.5 60 45 E   50 125   3-6 10 3     ET-.sup.(5)  10%EA 13 4-6 50-100 20-50 G G     G  1 40 90   1 3-7 4 ET-     20% EA 13 4-6 50-100 20-50 G G     G 13 ET-.sup.(6)  IsoBA 13 4-6 50-100     20-50 G E     F.sup.(19) 14 Saran.sup.(7) 13 6-10 50-100 50-100 G E     E     34 34 15 ET-  33% VA 27 4-9 50-100 20-70 G E     E  3-7 16 ET-     33% VA 17 4-7 50-100 20-70 G E     E 17 ET-  20%EA 17 4-7 50- 100 20-50     G G 13.1 9.0   E 11 3-6  47 41   13-16 18 ET-  20%EA 17 4-7 50-100 20-50     G G     E 30 None.sup.(7) 13  25-150  G  12.0 12.0 60 60 E 1 1 100 18 18     1 1 31 None 17  25-150  G  10.0 10.0 80 80 E 18 3 150 35 35 1 2 12-19     .sup.(1) Extrusion     Good - could make continuous roll of film.     Fair - could make bubble sections only.     .sup.(2) Bond     Excellent - could not separate films with tape.     Good - could separate films with tape.     Fair - could separate films by scraping cross-sectional area with razor     blade.     .sup.(3) Film Clarity     Excellent - clear.     Good - slight haze.     Fair - medium haze distorts objects     5 feet away.     .sup.(4) Ethylene-vinyl acetate.     .sup.(5) Ethylene-ethyl acrylate.     .sup.(6) Ethylene-isobutyl acrylate.     .sup.(7) Control     .sup.(8) Good     .sup.(9) Excellent     .sup.(10) Fair     .sup.(11) Lengthwise      .sup.(12) Crosswise     .sup.(13) Grams     .sup.(14) Pounds per square inch.

Referring to Table I, the results are best discussed in terms of thoseposted in the table.

In runs 1 to 4, 13, 14 and 30, saran was of the commercial type, that isthe household film polymer sold as Saran Wrap by Dow Chemical Company,Midland, Michigan.

Runs 15 to 18 and 31 utilized the shrink bag type saran usually used inturkey bag and chicken bag applications.

In runs 1 and 2, the ethylene-vinyl acetate copolymer was extruded asthe outer layer. The latter is a much softer and tackier plastic thanregular saran. The bond between the two plys is excellent and the filmsare heat-sealable.

In winding up the laminated film, a slip sheet could be used to preventthe copolymer from blocking. Blocking agents could also be used to makesaid copolymer less tacky. Conversely, the tackiness of the unsaturatedester copolymer makes it an excellent adhesive layer for other films,paper, or metal and this is described below.

In runs 3 and 4, the ethylene-ethyl acrylate extruded with the greatestease in conjunction with saran. However, this combination does not haveas much bond between the two films as is desirable. An ethylene-vinylacetate layer between the two would, because of its tackiness, providethe necessary glue layer to effect an excellent three-ply laminate, andsuch a laminate is described below (see Example II).

Run 13 illustrates the use of ethylene-isobutyl acrylate as thecopolymer. It produces an excellent film bond with good extrudability.

The O₂ gas transmission values of Table I reveal that the gastransmission, in general, follows the type of saran used.

The percent shrink also seems to follow that of the saran used. Thus, ifa shrink type saran is used, the shrink characteristics of the resultantlaminate are similar.

High frequency heat sealing of bags where the ethylene-unsaturated estercopolymer is on the outside was successful. This is a most unique andhighly desirable result, and was unexpected since ethylene-unsaturatedester copolymers cannot normally be high frequency sealed.

The cold flex is also improved over saran. In addition, the filmsproduced are clear. A good bond is effected between the layers and sincesaran constitutes one layer, a good barrier film is therefore produced.The films of these Examples also have considerable strength and retaintheir shrink characteristics.

EXAMPLE II THREE LAYER LAMINATE

In this Example, the innermost layer (of the tube or bubble) is saran, amatrix which gives desirable bubble forming characteristics andfurnishes excellent barrier properties in the finished film. The middlelayer is ethylene-vinyl acetate for a glue layer, and cold temperatureproperties in the finished film. The outer layer of the tube or bubbleis composed of ethylene-ethyl acrylate. This layer providesanti-blocking, low temperature properties and heat sealability to thefinished film.

The die that is used in making this three-layered film is shown in FIG.2. In this instance, all extrusion slits are used. The saran is fed by afirst extruder (not shown) into slit 12. At a lower point, the saran iscovered by ethylene-vinyl acetate fed from manifold 24 into slit 16 by asecond extruder. The combination of saran and ethylene-vinyl acetateflow downward and in turn are covered by ethylene-ethyl acrylate fedfrom manifold 22 into slit 14 by a third extruder. The combinedextrudate exits from the 17/8 diameter exit slit 17 as a molten tube.

Thereafter, the procedure follows essentially the same procedure withsimilar equipment as that used in making the basic laminate of ExampleI. The main differences are:

1. An additional extruder because of the the third ply.

2. Higher bath temperatures in the hot bath for blowing the exteriorpolyolefin.

3. Air cooling ring around blown bubble to remove excess heat afterorientation.

Films of 50 to 300 gauge may be produced by the method of this Example.The thickness ratio of the saran to the total thickness of the secondaryand tertiary films usually runs about 2:1. The ratio of the secondaryand tertiary layers to each other is usually about 1:1.

Tubing widths from 12 to 17 inches, and greater, are possible.

In regard to gauges and widths, either one may be altered by theexpansion of the oil sock and/or the speed of the train and of course alarger die could be utilized.

Extrusion rates are generally in the range of 40 to 50 lbs/hr., total,for all three extruders. The rates of the extruders feeding thesecondary and tertiary layers are usually 6 to 8 lbs/hr. each.

In co-extruding the three-layered film, saran appears to be the primarylayer. This layer is cooled by the sock fluid and remains amorphousuntil blown. It forms the matrix of the bubble which resembles thatfound when making regular saran film. This layer provides tensile andbarrier properties and high shrink if shrink-type saran is used.

The secondary layer (center glue layer) of ethylene-vinyl acetate issoft and tacky; it flows readily and is less affected by temperaturechanges in the baths. Evidently this layer glues the other layerstogether.

The tertiary layer, or the layer exposed to the baths, is ethylene-ethylacrylate. This plastic must be reheated in the hot bath before it willallow the bubble to be blown. It is necessary to then remove this heatby air cooling the bubble and establish an expanded end-point. Thislayer aids in sealability and low temperature properties.

EXAMPLE III THREE LAYER LAMINATE

In similar fashion as Example II, the die of FIG. 3 is also useful. Itis designed to put the saran layer in the center position of thethree-layer laminate. The inner layer is ethylene-ethyl acrylate and theouter layer is ethylene-vinyl acetate. The only variation over theprocedure of Example II is in the cooling and reheating of the layersfor tube expansion.

EXAMPLE IV THREE LAYER LAMINATE

A reversal of outer and inner layers with the ethylene-vinyl acetateextruded to form the inside layer is also effective, but it blocks sobadly that unless blocking agents are blown into the sock through diehead 10 or slip sheets are used, or saturated amides are blended intothe ethylene-vinyl acetate, the tube cannot be opened for subsequentblowing.

It might be noted that the blown bubble has a tendency to curl away fromthe saran when the tube is opened. This makes it difficult to work with.A thinner layer of ethylene-vinyl acetate obviates some of this problem.A post-treatment consisting of passing the reblown bubble through a heattunnel or over hot rollers also improves this curl problem greatly.

Representative films are made, then subjected to physical tests. Theresults shown in Table II are typical data from such tests.

                                      TABLE II    __________________________________________________________________________    PHYSICAL PROPERTIES OF THREE LAYER LAMINATE                 TENSILE STRENGTH      DART DROP COLD                                                     O.sub.z                                                          % SHRINK                 PSI (in Thousands)                             % ELONGATION                                       -18° C                                                 FLEX                                                     cc/100                                                          100° C 1 MIN     FILM   GAUGE                 L.sup.(1)                       C.sup.(2)                             L    C    66 cm     -18° C.                                                     sq.in./mil                                                          L   C    __________________________________________________________________________    Saran (control)            200   8,000                       10,900                             120  135  600 gm    1   16   41  41    Saran (control)            150  12,000                       12,000                              60   60  300 gm    1   1.0    2-Layer Saran    (control)            200  11,200                       12,600                             117  138  300 gm    1    3-Layer Saran            205   8,200                       7,900 148  138  Et-EA up = 1150 gm                                                 6   13   40  41    Et-VA(3)                           Saran up = 600 gm    Et-EM(4)    3-Layer Saran            200   8,900                       8,600 230  170  Et-VA up = 3000 gm                                                 6    Et-VA                              Saran up = 1600 gm    Et-EA    3-Layer Saran            200  11,000                       10,000                             107  112  Et-VA up = 1100 gm                                                 +1  1.7    Et-VA                              Saran up = 700 gm    Et-EA    __________________________________________________________________________     .sup.(1) Lengthwise     .sup.(2) Crosswise     .sup.(3) Ethylene-vinyl acetate copolymer     .sup.(4) Ethylene-ethyl acrylate copolymer

From Table II, it is evident that three-layer films made via Examples IIto IV have:

1. Such excellent layer bonding that they cannot be separated.

2. Cold temperature properties that are not attainable in regular saranfilms.

3. A broader and lower range of heat seal temperatures over thoseobtainable with regular saran with improved seal strengths.

4. Tensile, elongation, barrier and shrink properties essentiallyidentical to regular saran.

Table III which follows shows some of the uses of such three-layer filmand the advantages therefrom.

                                      TABLE III    __________________________________________________________________________    USES OF THREE-PLY LAMINATE     APPLICATION               ADVANTAGES        PRIOR PRODUCT    __________________________________________________________________________    Air Duct Covering               Better toughness, self-extinguishing                                 200 gauge saran               tear, snag and puncture resistant    Cheese Curing Block               Manufacture by layered extrusion                                 (1) saran films               rather than hot combining                                 (2) wax/cellophane/foil/                                   polyethylene laminate                                 (3) saran/polyethylene                                   "cling" product    Bags       Tougher outer layer - better                                 Saran               abrasion resistance and low tempera-               ture toughness    Candy Bags Good barrier - good sealability-                                 Saran               eliminate combining operation and               dusting    __________________________________________________________________________

The Examples which follow illustrate further such processing and uses ofthe basic laminate and/or the three-layer laminates of Examples II toIV.

EXAMPLE V LAMINATION TO PAPER AND BOTTLE CAP LINER

The basic laminate 100 (FIG. 4) of vinylidene chloride-vinyl chloridewith ethylene-vinyl acetate of Example I with the latter polymer as theadhesive is laminated to paper 102 using the apparatus of FIG. 4. It islaminated to paper 102 as a strip (about 5 to 12 inches wide), whichavoids the need to manufacture wide webs, by passage between heated(about 200° F) roll 104 and press roll (about 25 psi) 106. If desired,the paper used can be preprinted. The heat marries the ethylene-vinylacetate to the paper. Dielectric heat sealing of the pressed laminatepaper may also be utilized to marry the two together.

The resultant coated paper 108 may be wound onto windup roll 110 forsubsequent use, or it may be utilized on a bottle cap liner makingmachine. The latter utilizes a punch 112 and a die 114 to stamp outbottle cap liners 116 from the coated paper 108. With the saran layerup, an excellent bottle cap liner is produced.

Saran and other plastic film coated with a pressure sensitive adhesivehave been used as protective coverings for polished surfaces such aschrome-plated steel. Unfortunately, the sensitivity of the organic filmto direct sunglight causes the film to degrade, and has prevented widescale adaptation of such use.

EXAMPLE VI LAMINATION TO METAL AND USE AS PROTECTIVE COVERING

The basic laminate of Example I is married to aluminum or other metalfoil such as tin-plated steel with the saran side outward. This metallaminate, with the metal side outward, is then used to coatchrome-plated steel sheets. To do so, the metal is slightly warming andthen the laminate is rolled onto the surface of the chrome-plated steelsheet using a suitable pair of rubber/steel rolls. Thereafter, suchcoated chrome-plated steel is used for exterior construction while thelaminate is adhered thereto. In this way, the chrome-plated steel sheetis protected. After installation, the laminate is peeled off.

In tests to compare the resistance to sunlight, samples of saran coatedchrome-plated metal are exposed for thirty days in Florida sunlight. Thesaran film on the chrome-plated metal decomposed and either becamedifficult to remove or corroded the metal. When a metal laminate such asdescribed above is used as above, no decomposition will be noted,probably because the film is protected or shaded by the metal foil whichis laminated thereto as the outer covering.

EXAMPLE VII TRAPPED LABEL LAMINATE-CHUB USE

Referring to FIGS. 5 and 6, two sheets 120 and 122 of the basic laminateof Example I (with the ethylene-vinyl acetate comprising about 8 to 36%vinyl acetate in said copolymer of a melt index of 2 to 30) having theirethylene-vinyl acetate sides facing each other, are passed between twopress rolls 124 and 126 which may be heated or used in conjunction withdielectric heating means. Prior to such passage, a continuous length ofprinted polyethylene 128 (or other films, paper, textile or foil) is putbetween the two sheets. A discontinuous array 131 of labels may also beused. It will be found that trapping of the foreign film, paper or foilis perfectly made. There is no slipping of the label during use asfrequently occurred where mono-layer saran was used with a label trappedtherebetween.

Operative limits are as follows: Roll pressure -- as found in usualrubber-metal nip rolls. Temperature -- approximately room temperature to175° F. Rate -- ordinary film combination rates of 1 to 200 f.p.m.

Label variants are as follows:

Ethylene-unsaturated ester type copolymer, vinyl chloride, polyester,polyethylene, polypropylene, cellophane, paper, textiles, foil and otherweb material.

Of the ethylene-unsaturated ester type copolymer, ethylene-vinyl acetatewill be found to be the easiest processing tack polymer which can beused for trapped label work. To permit unwinding from the supply roll, asaturated amide (i.e. stearamide), in percentages of 0.05 to 1.0%,dependent on the thickness of the olefin layer and the slip andanti-block characteristics of the saran, is best, because it has theleast adverse effect on clarity. Other finely divided inorganic powderssuch as calcium carbonate, or tetra sodium pyro phosphate are alsoeffective to a much smaller degree, unless combined with a saturatedamide. Layer thicknesses of greater than 0.00003 (3 gauge) inches shouldbe used to effect necessary laminating characteristics.

With respect to the saran, a high slip additive content saranformulation is used. The trapped label laminate may then be useddirectly in a chub making machine, such as that made by Kartridge-Pak,807 Kimberly, Davenport, Iowa.

The principal element of the usual chub machine comprises guide rolls129 and 130, a hollow tube former 132 with a stuffer 134 extendingtherethrough. The former 132 forms the tube, which is longitudinallysealed by a high frequency or hot air sealer 136. The tube is thenstuffed with product and then clipped into chub length.

EXAMPLE VIII CHEESE CURING BLOCK OVERWRAP

The laminate of Examples I and V are used to wrap cheese blocks. Athree-layer film utilizing a saran core and an ethylene-vinyl acetatecoating on both surfaces could also be utilized for this applicationprovided blocking agents are used in the outer ethylene-vinyl acetatecoating. The overlapped ends are folded in the manner shown in FIG. 7.The blocks wrapped with the laminate of Example I have theethylene-vinyl acetate layer on the outside. The blocks wrapped with thelaminate of Example V have the paper layer on the outside. The paperlayer increases the strength of the inner saran layer and permits theremoval of both paper and the saran laminate at one time and in onepiece, thus saving time and labor. Previously, two wrappers, one of filmand one of paper, were used.

The blocks wrapped in the laminate of Example I, when inspected after aone-month storage period, will exhibit no mold. Inspection of the blockswrapped with the laminate of Example V cannot be made because of thepaper overwrap which is sealed to the film, unless the wrapper isdestroyed. However, when completely unwrapped, similar results will beevident.

Table IV which follows shows some results of use of the laminate ofExample I as cheese curing block overwrap:

    TABLE IV      CHEESE CURING BLOCK OVERWRAP          Boiling   Lengthwise Crosswise  Water Meat Seal  Ethylene   2%   2% D     art % Shrink    Peel Run Unsat. Tensile % Secant Tensile % Secant Impact 1     00° C O.sub.2 Gradner Test Temp Strength No. Gauge Saran Ester     Strength Elongation Modulus Strength Elongation Modulus 25° C     -18° C L Trans Clarity Hazel Gloss °      F (16 sq/in)            1 75(1) commercial ethylene-28% 11,300 41%     74,600 13,200 46% 71,400   26% 14%  90 1.3 100+ 145 .34   household VA +     0.5% psi   psi  psi        both 185 2.05    stearamide     sides 225 2.19    +.07%               265 2.72    particles      305 3.50 2 75(1) commercial same 12,000 55% 55,500 13,000 51% 50,000     5.17  28% 24%  97 1.5 100+ 145 .83   cheese  psi   psi  psi g/cm/mil       both 185 1.34   wrap               sides 225 1.58     265 1.31                   305 1.35                   345 1.55             355 2.47 3 75(1) commercial ethylene-28% 10,000 44% 63,500     14,400 57  50,000 5.78  25% 23% .87 99 1.5 100+ 145 .41   cheese VA +     1.0% psi   psi  psi     cc/100   both 215 .78   wrap stearamide     sq. in.   sides 275 .74    +0.7%               355 .90    particulate     material 4 79   same --  8,400 58% 69,200 10,300 35  57,700 6.05  20%     15% 1.31 86 1.7 100+ 215 .03              cc/100   both 245 .17          sq. in.   sides 295 .32     (1) 60 saran, 15 EVA

From the above tests and others, it will be found that ethylene-vinylacetate (28%) copolymer is the most effective for the heat sealpackaging of cheese. While other vinyl acetate levels may be effective,they must be especially formulated to permit unwinding from mill rollsand yet maintain the correct cling level. Again, stearamide, (0.05% to3% by weight, dependent on the thickness of the olefin layer and theslip and anti-block characteristics of the saran layer) can be used asan anti-blocking agent. The other finely divided inorganic powders,(calcium carbonate, tetrasodium pyrophosphate) may also be used.

If the layer thickness of the ethylene-vinyl acetate is increased up to0.00040 inches, the effectiveness of the heat seal will also increase. Aheat sealing temperature range of about 165° F to 355° F with 0.00010inches ethylene-vinyl acetate/0.00070 inches saran is effective, whereasregular saran seals are about four times weaker and heat seal range isonly about 260° F to 280° F.

This new material makes it possible for the first time in the history ofsaran for a saran type film to compete in a market which before wasalmost entirely dominated by wax/cello/foil laminates. It can be heatsealed in any of the conventional manners including the use of electrichot plates, electric or hot water presses, and by placing the wrappedblocks in the cheese hoops and spraying them with hot water or steam.

EXAMPLE IX FORM, FILL AND SEAL

As illustrated in FIG. 8, the saran laminate of Example I is used onform, fill and seal equipment for packaging powdered and granulatedproducts. Such equipment utilizes as its basic components two formingrolls 140 and 142 with depression 143 therein to form the package 144.The rolls are heated to seal the laminates (the ethylene-vinyl acetatelayer of each facing outwardly) as the product 146 is sealed therein.The equipment utilized can be:

Triangle Package Machinery Company

6655 W. Diversey Ave.

Chicago, Illinois 60635

Hayssen Manufacturing Co.

P. o. box 571

Sheboygan, Wisconsin 53081

Bartelt Engineering Co., Inc.

Subs. of Riegal Paper Corp.

1900 Harrison Ave.

Rockford, Illinois 61101

Fmc corporation

Canning Machinery Div.

333 West Julian St.

San Jose, California 95108

Hesser Fr. Machinenfabrik Aktiengelsellschaft

Neuheimer Strasse 99

Stuttgart-Bad Cannstadt

Germany

Mira-Pak, Inc.

7000 Ardmore

Houston, Texas 77021

Package Machinery Company

330 Chestnut St.

East Longmeadow, Mass. 01028

Wright Machinery Co.

Div. of Sperry Rand Corp.

Calvin and Holloway Sts.

Durham, N.C. 27201

standard Packaging Corporation

Flexible Packaging Division

1 Lisbon St.

Clifton, N.J. 07015

these utilize heat and impulse sealers of the usual type and it might benoted that in the past, saran could only be high frequency,electronically sealed, using these machines. Thus, the laminate of thisinvention now enables heat sealability never heretofore possible.

Heretofore, pouches for maximum barrier use comprised polyethylenecoated or laminated to aluminum foil. The polyethylene surfaces wereheat sealed together at the edges to make the pouch.

EXAMPLE X POUCHES

Aluminum foil and the basic laminate of Example I with the saran facingoutward are laminated together following the method of Example V. Then,two such aluminum foil (ethylene-vinyl acetate) saran laminates areformed into pouches using equipment such as shown in FIG. 8. The pouchformed therefrom will furnish a maximum barrier foil pouch since theseal area is saran. Furthermore, any pinholes in the aluminum will becovered essentially by saran which is a high barrier film.

The aluminum foil used can be of the rigid or flexible variety dependingon the package demands. Since saran can be extruded quite thinly, (inthe range of 25 gauge), and since the ethylene-vinyl acetate layer canbe as thin as 10 gauge or less, if desired, (at least enough to providea bond), a relatively thin aluminum laminate can be produced even thoughaluminum pinholes increase inversely as the thickness. The better"pinhole plugging" capacity of the high barrier saran enables use ofaluminum foil as low as 23 gauge.

The advent of thin tin-coated steel sheet also makes such foilpossibility. Combinations of the tin-coated sheet of 50 gauge thicknessmade with ethylene-vinyl acetate and saran are as effective as otheraluminum foil.

Use tests reveal that a superior pouch material, better than now on themarket, has been produced. Shelf life is increased and flavors arebetter preserved in the package. Resistance to oils and chemicals isalso greater.

EXAMPLE XI VACUUM DRAW

The low cost basic laminate of Example I is used in a vacuum drawprocess to form webs such as illustrated in FIG. 9, on customary drawmachines such as:

Mahaffy 614

Mahaffy and Harder Engineering Co.

Newark, N.J.

standard Packaging 612

Standard Packaging Corporation

Flexible Packaging Div.

1 Lisbon St.

Clifton, N.J. 07015

and others. Similarly, pressure forming, or vacuum draw with a plugassist would also be used since these are mere variants on a vacuum formtechnique.

The laminate gauge thickness may be 0.5 to 4.0 mils.

In such operation, it will be found that the basic laminate of Example Ihas good drawability to 2 inches. It has excellent optical propertiesbefore and after forming. And the resultant formed item is readily heatsealed especially if the ethylene-vinyl acetate was selected to seal attemperatures of about 200° F.

Compared to the known art which teaches use of a laminate of mylar ornylon with a saran coating, the mylar is limited in draw depth to 1inch, and the nylon is very expensive and not optically attractive.

EXAMPLE XII PAPERBOARD AND PACKAGING

The laminate of Example I (at least 50 gauge saran with 5 gaugeethylene-vinyl acetate) is laminated to paperboard with heat andpressure -- the ethylene-vinyl acetate side to the paperboard.

The resultant saran coated paperboard is then formed into containers,such as milk cartons or cereal boxes. The saran provides a barrier forgreases and gases and moisture. Such containers can be hermeticallysealed by dielectric sealing provided a saran to saran contact can bemade.

Alternatively, the laminate of Example I could be thermoformed and thenlaminated to paperboard, as in the blisterpack, skin pack, pre-fabflexible blisterpack, or stretch film pack techniques. This film can beprinted on either side prior to lamination. In effect, the printingcould be trapped or on the surface, and the lamination could be on oneor two sides of the paperboard.

Since a saran of shrinkability may be used, it should also be evident,as seen, for example, in Example XII above, that many of the abovearticles may be subjected to a post-treatment whereby the laminate ofExample I or its derivatives, as described above, are shrunk.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above article and method andconstruction without departing from the scope of the invention, it isintended that all matter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustrative and not ina limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statments of the scope of the invention, which, as amatter of language, might be said to fall therebetween.

Now that the invention has been described:

What is claimed is:
 1. A pouch comprising two sheets of a bilaterallyoriented plastic laminate comprised of a first layer of a vinylidenechloride-vinyl chloride copolymer containing a predominant amount ofvinylidene chloride in the copolymer molecule, and a second layer of anethylene-unsaturated ester type copolymer containing a predominantamount of ethylene in the copolymer molecule and wherein saidunsaturated ester is selected from the group consisting of vinyl acetateand isobutyl acrylate, said first layer and said second layer beingnon-separable with tape and said laminate being prepared by coextrudingsaid first layer and said second layer as a plural layered tube,chilling said tube at a temperature of about 5° C to about 25° C andthen tempering said tube at a temperature of about 20° C to about 50° Cimmediately prior to blowing said tube into a bubble with a fluidwhereby the molecules of said copolymer are bilaterally oriented andwherein the total area of said bubble is at least about 16 times thearea of said tube, said layer of vinylidene chloride-vinyl chloride ofone laminate being joined to said layer of vinylidene chloride-vinylchloride of the other laminate to form said pouch.
 2. A plastic troughhaving wall and base portions formed of a bilaterally oriented plasticlaminate comprised of a first layer of a vinylidene chloridevinylchloride copolymer containing a predominant amount of vinylidenechloride in the copolymer molecule, and a second layer of anethylene-unsaturated ester type copolymer containing a predominantamount of ethylene in the copolymer molecule and wherein saidunsaturated ester is selected from the group consisting of vinyl acetateand isobutyl acrylate, said first layer and said second layer beingnon-separable with tape and said laminate being prepared by coextrudingsaid first layer and said second layer as a plural layered tube,chilling said tube at a temperature of about 5° C to about 25° C andthen tempering said tube at a temperature of about 20° C to about 50° Cimmediately prior to blowing said tube into a bubble with a fluidwhereby the molecules of said copolymer are bilaterally oriented andwherein the total area of said bubble is at least about 16 times thearea of said tube, said second layer forming the lining of said trough.3. A wrapped cheese curing block comprising a block of cheese wrapped ina bilaterally oriented plastic laminate comprised of a first layer of avinylidene chloridevinyl chloride copolymer containing a predominantamount of vinylidene chloride in the copolymer molecule, and a secondlayer of an ethylene-unsaturated ester type copolymer containing apredominant amount of ethylene in the copolymer molecule and whereinsaid unsaturated ester is selected from the group consisting of vinylacetate and isobutyl acrylate, said first layer and said second layerbeing nonseparable with tape and said laminate being prepared bycoextruding said first layer and said second layer as a plural layeredtube, chilling said tube at a temperature of about 5° C to about 25° Cand then tempering said tube at a temperature of about 20° C to about50° C immediately prior to blowing said tube into a bubble with a fluidwhereby the molecules of said copolymer are bilaterally oriented andwherein the total area of said bubble is at least about 16 times thearea of said tube.
 4. In a laminated structure: a bilaterally orientedplastic laminate comprised of a first layer of a vinylidenechloride-vinyl chloride copolymer containing a predominant amount ofvinylidene chloride in the copolymer molecule, and a second layer of anethyleneunsaturated ester type copolymer containing a predominant amountof ethylene in the copolymer molecule and wherein said unsaturated esteris selected from the group consisting of vinyl acetate and isobutylacrylate, said first layer and said second layer being non-separablewith tape and said laminate being prepared by coextruding said firstlayer and said second layer as a plural layered tube, chilling said tubeat a temperature of about 5° C to about 25° C and then tempering saidtube at a temperature of about 20° C to about 50° C immediately prior toblowing said tube into a bubble with a fluid whereby the molecules ofsaid copolymer are bilaterally oriented and wherein the total area ofsaid bubble is at least about 16 times the area of said tube; and alayer of material selected from the group consisting of paper,paperboard, metal and metal foil adherent to said plastic laminate. 5.Bottle cap liners comprising appropriately shaped portions of thelaminate of claim 4, wherein said layer is paper and said layer ofethylene-unsaturated ester type copolymers is between the paper and thelayer of vinylidene chloride-vinyl chloride copolymers, and the latterfaces the interior of the bottle when in use.
 6. A wrapped cheese curingblock comprising a block of cheese wrapped in the laminate of claim 4wherein said layer is paper and is on the outside.
 7. A protectedornamental flat surface comprising the surface of an object havingadhered thereto the laminate of claim 4 wherein said layer is metal foiland is on the outside.
 8. A trapped label laminate comprising two sheetsof a bilaterally oriented plastic laminate and a printed labeltherebetween, each of said sheets being comprised of a first layer of avinylidene chloride-vinyl chloride copolymer containing a predominantamount of vinylidene chloride in the copolymer molecule, and a secondlayer of an ethyleneunsaturated ester type copolymer containing apredominant amount of ethylene in the copolymer molecule and whereinsaid unsaturated ester is selected from the group consisting of vinylacetate and isobutyl acrylate, said first layer and said second layerbeing non-separable with tape and said laminate being prepared bycoextruding said first layer and said second layer as a plural layeredtube, chilling said tube at a temperature of about 5° C to about 25° Cand then tempering said tube at a temperature of about 20° C to about50° C immediately prior to blowing said tube into a bubble with a fluidwhereby the molecules of said copolymer are bilaterally oriented andwherein the total area of said bubble is at least about 16 times thearea of said tube, said first layers of said sheets being on the outsideof said label laminate.
 9. A package comprising the label laminate ofclaim 8 sealed longitudinally and clipped at both ends.